1. Field of the Invention
The present invention relates to a display device. The invention particularly relates to a technique of facilitating the inspection for signal interconnects formed in the region outside detection and display areas for the display device.
2. Description of the Prior Art
A liquid crystal display panel is configured such that a first substrate is opposed to second substrate by way of a liquid crystal layer, in which the first substrate (TFT substrate) is formed with thin film transistors, pixel electrodes, etc. and the second substrate (color filter substrate) is formed with color filters, etc. The liquid crystal display panel having such a structure is manufactured as follows. The first substrate (TFT substrate), which contains circuit patterns for the liquid crystal display devices by a plurality number of sheets, is bonded to the second substrate (color filter substrate) including color filters, etc., where liquid crystals are sealed between the substrates. The thus-formed glass substrate is then cut on every liquid crystal display device. If chipping or crack is formed at the end of the glass substrate at the cutting step or during handling of the glass substrate, a problem with interconnect defect arises in which signal interconnects formed over the substrate are disconnected at the same time with occurrence of substrate chipping or cracking.
In a display device mounted on a mobile information terminal, a coordinate input device referred to as a touch panel is attached to the liquid crystal display panel on the side of the display surface and so image display is generally controlled based on the information provided by the display image and the contact position. The touch panel has such a structure that electrodes are formed in a detection region over a glass substrate and signal interconnects for supplying driving signals to the electrodes are formed at the periphery of the detection region. Accordingly, a problem with interconnect defect arises in which the signal interconnects are disconnected at the same time with occurrence of substrate chipping or cracking as is the case with the liquid crystal display panel.
JP-A-2002-350896, for example, discloses a liquid crystal display device as a method of detecting such interconnect defect. The liquid crystal display device described in JP-A-2002-350896 is configured as follows. Common interconnects arranged in parallel are connected to each other at the peripheral edge portion of the display screen and the display screen is formed with an opening at a central portion thereof, thereby enabling detection of disconnection of the common interconnects using an array technique.
Further, JP-A-1997-80478 discloses a technique of detecting short-circuit of drain lines by using a provisional interconnect formed in parallel with gate lines. Further, JP-A-1995-152043 discloses a technique of forming a liquid crystal display device pattern by a plurality number of sheets per one glass substrate. In such a technique, when the glass substrate is divided into liquid crystal display devices at a cutting step, common interconnects for connecting interconnects to each other are provided for regions where the liquid crystal display devices are separated.